Porous slide bearings are mainly used in motors for household electric appliances, automotive motors and the like. A bearing of this type is made of a sintered compact having pores impregnated with a lubricating oil which oozes out onto the sliding surface during use, thus extending the bearing's working life.
A porous slide bearing is normally made of a sintered compact having a homogeneous porous structure obtained by subjecting the compact to such treatments as mixing, press molding, calcining or forming finely powdered grains of iron, copper, zinc, tin, graphite, nickel or an alloy thereof. Such a sintered compact usually has pores 50 microns or less in diameter (many of them are 10 microns or less).
In order to permit use of such a porous slide bearing for a prolonged period, its pores have to be impregnated with a sufficient amount of lubricating oil. However, since it is kept inside the pores of the sintered compact only by the action of surface tension and viscosity, a decrease in viscosity might happen together with an increase in volume due to frictional heat in the bearing or in a high-temperature environment, causing the lubricating oil to flow out of the bearing. Thus, the range of operating temperatures is restricted and the durability of the bearing can drop.
In order to solve these problems, with a bearing which is required to have a long life, it is necessary to provide an oil tank made of felt or wick and keep it in contact with the outer surface of the bearing.
But if such means is employed in applications where any oil stain is undesirable, it is necessary to provide a seal to prevent oil leakage. This will restrict the freedom of the design and increase the cost.
It is an object of this invention to provide an oil-containing bearing which can prevent the leakage of lubricant by use of simple means without using an oil tank.